The test "test_normalization" download a file from the "unicode.org" website and keep it in the local cache "Lib/test/data/" directory for next runs.
On test setup, it verifies if the 1st line contains the right version "unicodedata.unidata_version".
It should unlink the file if it is outdated.
But it does not work as expected: it looks for the file in the wrong directory.
~ $ echo "# NormalizationTest-3.0.0.txt ~ outdated version" > Lib/test/data/NormalizationTest.txt
~ $ ./python -m test.regrtest -uall test_normalization
test_normalization
test test_normalization failed -- Traceback (most recent call last):
File "./Lib/test/test_normalization.py", line 96, in test_main
self.assertTrue(X == NFC(X) == NFD(X) == NFKC(X) == NFKD(X), c)
AssertionError: 160
1 test failed:
test_normalization
~ $ cat Lib/test/data/NormalizationTest.txt
# NormalizationTest-3.0.0.txt ~ outdated version

Here is a patch.
The function "test_support.open_urlresource" is enhanced with an optional argument "check" which receives a function. This "check" function accepts an open file as input and return False if the file is outdated.